Without NASA's planetary missions we wouldn't be in orbit at both asteroid Vesta and planet Mercury. We wouldn't see stunning close-up images of comet nuclei. We would not know that there is evidence for water on Mars, nor that Enceladus' ice-shooting "Tiger Stripes" provide the water found in Saturn's upper atmosphere. Nor would we know that possibly at the edge of our solar system there are gigantic magnetic bubbles.

This is a busy year for NASA -- one of its busiest. There are several missions launching and many which are currently in flight or in development/production. Every mission takes several steps and many people to prepare it for flight in space. And each step is important for the success and successful science return of a mission.

For example, takes the case of NASA's Mars Science Laboratory's rover, Curiosity, which will launch on 25 November. It has been a long process: from the proposal stage, back in 2003; to design, beginning in 2004; to the construction of the spacecraft's parts following about 12 to 18 months later. The various components are now being tested at the Kennedy Space Center (KSC) and it won't be until next month, when Curiosity is enclosed in its aeroshell, will engineers and technicians stop tinkering with the newest Mars rover on the block.

With careful planning and execution NASA returns to us great data and images of places seen and visited by spacecraft. See below for images that demonstrate the testing and planning that goes into building these far-traveling explorers. (13 images total)

Juno Spreads its Wing: Technicians test the deployment of one of Juno's three massive solar arrays. This critical test simulates flight-like conditions, with the spacecraft's own electronics providing the command to deploy the array.
(Juno launched for Jupiter on 5 August 2011.)
Image Credit: NASA

Spacecraft Care: At Astrotech, a Dutch Space technician repairs a small damaged section on the lower edge of the solar array panel on the Dawn spacecraft. The damage occurred during a procedure to prepare the Dawn spacecraft for spin-balance testing. The size of the affected area was about 2.5 inches by 2 inches. (Dawn is currently in orbit at asteroid Vesta.)

The heat shield for MSL is the largest ever built for a planetary mission. The heat shield and back shell, which together form the spacecraft's aeroshell, have a diameter of 4.5 m (nearly 15 feet). The aeroshell will encapsulate and protect Curiosity from intense heat and friction generated during descent through the Martian atmosphere. (MSL will launch for Mars on 25 November 2011.)

Image Credit: NASA/JPL

Spin Cycle: The blurred image of the New Horizons spacecraft is the result of a spin test that was conducted in the Kennedy Space Center's Payload Hazardous Servicing Facility as part of New Horizon' prelaunch processing. Try this: Stare at New Horizons in this image and then quickly glance to the right without moving your head. Did the spacecraft move when you shifted your gaze? (New Horizons is currently in flight and expected to reach Pluto in July 2015.)

Image Credit: NASA

Check-Up: Technicians prepare to hoist one of the two GRAIL spacecraft upon completion of a thermal vacuum test at the Lockheed Martin Space Systems facility in Denver. (GRAIL will launch 8 September 2011.)

Solar Panel Cleaning: At Astrotech Space Operations in Titusville, Fla., the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft's two solar arrays underwent cleaning inspections and voltage checks in preparation for installation. (MESSENGER is currently in orbit about Mercury.)

Image Credit: NASA

Juno -- Almost Ready: This image shows NASA's fully assembled Juno spacecraft undergoing testing. All three solar array wings can be seen installed and stowed, and the spacecraft's large high-gain antenna in place on top.

Protective Shell: Technicians process the backshell for NASA's Mars Science Laboratory (MSL). The spacecraft's backshell carries the parachute and several components used during later stages of entry, descent and landing (EDL) of MSL's rover, Curiosity.

Image Credit: NASA/Jim Grossmann

Surrounded By Bunnies: (Yes, that is what we call the suits.) In the mobile service tower at Launch Complex 17-B, Cape Canaveral Air Force Station, workers move a panel into place above the MESSENGER spacecraft.

Image Credit: NASA

Honey Comb: Pictured here are the first six of 18 segments that will form NASA's James Webb Space Telescope's primary mirror for space observations.